Let's backup a step: it sounds like you're just beginning to prototype.
First, forget what the final, marketable product will be made out of--just get what's cheapest and easy to work with. Galvanized steel is a good choice. You might even be able to use PVC lined with aluminum foil.
Second, don't go buying any special, expensive metals--they're all going to end up in the trash in a month (if you're doing it right). RE-PURPOSE! Soup cans, coffee cans, soda cans, duct work from home depot, are all great CHEAP sources of materials. The container store is a bonanza. Get a flat nosed hammer, a hack saw, some tin snips, and a cheap pop riveter and go at it.
Then when you have a "proof of concept" you start the patent process.
And then when you have that locked down you start the marketable design that is more durable, easier to manufacture and specially crafted to not look like a tomato can priced at $30.
good luck and have fun with it